1. Field of Invention
This invention is directed generally toward rollers used on machines and more specifically toward rollers used on machinery in the harvesting of agricultural products.
2. Discussion of Related Art
Conveyors are commonly used during the harvesting and processing of agricultural products. Harvesters used in the harvest of such crops as potatoes, sugar beets, onions and carrots employ such conveyors. These conveyors are designed to shed dirt as they convey produce from the ground to the truck, for example. In processing applications, these conveyors also shed dirt, sand and other unwanted objects as they convey the produce. Examples of rollers employed with such conveyors are shown in U.S. Pat. Nos. 5,454,460 and 5,722,888. Due to the location required to support these conveyors, the dirt, sand and other materials shed from these conveyors tends to fall directly onto these rollers. Most often the rollers eventually fail due to contaminants getting to the bearings within the rollers. In fact, those rollers rarely fail for any other cause.
Prior art rollers are bored axially for the placement of radial ball bearings to support the load of the roller. Additionally, there may be other devices placed outboard of the bearing to offer greater sealing against contaminants. Typically, there will be a bushing placed through the bearing""s bore to size for an axle which is usually a bolt that attaches the roller to the frame of the harvester. These bushings typically extend beyond the length of the roller so as to stand the roller off from the frame of the harvester a defined distance. Axial bores in the prior art are parallel to the axle. Consequently, outer dimensions of bushings, also known as xe2x80x9cstandoffs,xe2x80x9d are then parallel to the axle. The dimensions of the standoffs or bushings are horizontal, allowing for an easy migration of contaminants along the topside of the standoff into the bearing housing.
Another problem existing with conventional rollers is with dirt or mud packing up on the standoff and eventually forcing its way beyond any additional sealing device and into the bearing bore. Eventually the contaminant gets into the bearings, causing the roller to fail.
Broadly speaking, this invention involves both aspects of the sealing of the roller, as well as directing contaminates away from areas where they would enter vulnerable parts of the roller, thereby causing the bearings to fail.
In a preferred embodiment of the invention, the roller assembly has an exterior portion adapted to support a conveyor element, and a bearing sub-assembly positioned within the exterior portion about a central axis. The bearing sub-assembly also has at least one bearing, at least one sealing element positioned outboard of the bearing and at least one standoff also positioned outboard of the bearing. The standoff also has a groove positioned on an outer surface thereof so that the groove can receive the sealing element therein.
In additional embodiments, the standoff may also have an inclined surface on an inboard side thereof. The inclined surface may be adapted for installing the lip, or elastomeric sealing portion of the sealing element gradually thereon without causing damage to it. Also the exterior portion of the assembly preferably has no surface that is parallel to the axis of the assembly. This allows for foreign material to be more readily shed off the surface of the roller assembly. Also preferably the diameter of the standoff is about the same as the diameter of the lip of the elastomeric sealing portion. In another embodiment, the horizontal length of the standoffs may be chosen so as to offset the exterior portion of the roller assembly at a predetermined distance with respect to the conveyor element.
In a preferred embodiment, the lip of the sealing element, which is also referred to herein as an elastomeric sealing portion, is reversed from the orientation used in prior devices. There is also a controlled distance between the elastomeric sealing potion and the vertical dimension of the standoff, thereby allowing a minimum amount of contamination to be trapped in this space. With the reversed lip on the oil seal, any particles finding their way into this cavity will serve to tighten the sealing lip against the standoff, producing an even tighter seal. However, the invention also comprises embodiments wherein the elastomeric sealing portion is in the orientation used in prior devices, although it is anticipated that in these embodiments, the sealing will not be as efficient.
In another preferred embodiment, the outboard surface of the standoff is sloped downward topside so as to convey dirt away from the bearings. The bore about the central axis of the roller also has a taper, which is wider at the outboard positions, thereby allowing gravity to assist with the elimination of any contamination that does get in the bore. Also preferably, the bore is configured so as to accommodate a snap ring without compression.